The term "effusive material" encompasses sufficient breadth to include any vaporizable or effusive material that may be desirably diffused within environment of a cathode ray tube, such as gettering or gas adsorbing substances, selected gases, and discrete metallic deposits. Such effusive material structures have been positioned at various locations within the tube to achieve maximum accomplishment of the desired results.
For example, in color cathode ray tubes, gettering structures have been affixed to the forward end of the electron gun assembly and projected by support means to position adjacent to the coated interior surface of the funnel. During tube processing activation of getters so positoned, the effusive material emanating therefrom is usually deposited over an expansive area of the funnel-disposed conductive coating.
In certain types of tube constructions, two or more diverse electrically-related coatings are adjacently disposed on discrete interior areas of the funnel portion. In such instances, the dispersal of a broad area of gettering material thereover becomes a deleterious factor in that it may effect electrical leakage between the coated areas. While diffusion directive means have been fashioned and incorporated with the getter containers to control the effusion of material emanating therefrom, there are times when adequate and consistent control is difficult to achieve, especially when the effusive structure is positioned proximal to the diversely coated areas. To minimize the above problem, the effusive structure, such as a gettering means, has been mounted in the forward region of the tube envelope on a screen related member, such as the color tube shadow mask structure, prior to sealing the face panel to the funnel portion of the envelope. This prior-to-sealing positioning of the exemplary gettering means evidences disadvantages in that the ambient atmosphere in conjunction with the heat required for sealing of the panel to the funnel produces a temperature-related environment which adversely affects the subsequent quality of the effusive material.